1. Field of the Invention
Embodiments of the present invention generally relate to isolation valves in wellbore completions. More particularly, embodiments of the present invention relate to flapper valves for isolating one casing region from another.
2. Description of the Related Art
Fracturing techniques in wellbores have been used to extract fluids, such as hydrocarbons like natural gas, from wellbores that would otherwise be unproductive. In situations where multiple hydrocarbon-bearing zones are encountered in vertical wells, horizontal wells, or in deviated wells, the multiple zones can be fractured one after another. This can be accomplished by perforating and then fracturing a distal zone and placing a bridge plug in the casing immediately above the fractured distal zone. This can isolate the fractured distal zone, allowing an adjacent proximal zone to be perforated and fractured. This process can be repeated until all of the desired zones have been fractured.
Once all the desired zones have been fractured, the bridge plugs between adjacent zones can be destroyed or opened to allow fluids from the fractured zones to flow in a commingled stream up the tube string to the surface. To accomplish this, the plugs can be broken apart or drilled out to allow the flow of fluid; however, this can leave fouling debris in the tube string and can present difficulties especially in deviated wells. Some plugs can instead be dissolved using activating agents, but this can limit the fluids that can be used with the downhole tool or present challenges if other dissolvable elements are used in the wellbore that are not intended to dissolve at the same time as the plug. The plugs can also be check valves, such as flapper valves, but the check valves need to be maintained in the open position during deployment down the well and thus require manipulation to allow them to operate at the desired time. This manipulation can require expensive equipment and can delay the sequential fracturing process. What is needed is a bridge plug that can effectively isolate the multiple zones, which can be deployed and removed without suffering from the drawbacks described above or others.